This application claims priority from Korean Patent Application No. 2000-30085, filed Jun. 1, 2000, the entirety of which is incorporated herein by reference.
1. Field of the Invention
The invention relates to a method for manufacturing a capacitor in a semiconductor device, and more particularly a method for manufacturing a capacitor in a semiconductor device in which a depletion of oxygen and a leakage current in a dielectric film can be suppressed.
2. Description of the Related Art
Recently, the need for memory elements had increased along with the development of techniques for manufacturing semiconductor devices. In a semiconductor device, a capacitor is used as means for storing data. The electric capacitance of such a capacitor depends on the electrode area and the dielectric constant of a dielectric film interposed between electrodes.
However, as semiconductor devices are highly integrated, the capacitor area given in the semiconductor device is reduced. Accordingly, the electrode area of the capacitor is decreased, thereby causing a reduction in the electric capacitance of the capacitor.
In order to solve this problem, a capacitor comprising a TaON thin film of high dielectric constant has been proposed, in which the TaON film has a metal film-insulating film-silicon (MIS) structure. As an upper electrode over the TaON thin film, a laminated structure of a TiN film/a polysilicon film is used.
FIG. 1 is a cross-sectional view illustrating a conventional method for manufacturing a capacitor with a TaON thin film in a semiconductor device.
As shown in FIG. 1, according to the conventional capacitor manufacturing method, a TaON thin film 2 having a high dielectric constant is deposited over a lower electrode 1, for example, a polysilicon film.
Then, a TiN/polysilicon film 3 having a laminated structure is deposited over the TaON thin film 2. The deposition of the TiN/polysilicon film 3 is achieved by forming a TiN thin film in a CVD (Chemical Vapor Deposition) chamber using TiCl4 as a precursor and NH3 as a reaction gas. Thus, a capacitor with an MIS structure is completely formed.
However, there are some problems involved in the conventional method for manufacturing a capacitor of a semiconductor memory device.
For example, when forming the TiN thin film in the CVD chamber using TiCl4 as a precursor and NH3 as a reaction gas during the formation process of the TiN/polysilicon film having a laminated structure conducted after the deposition of the TaON thin film having a high dielectric constant, oxidation may occur between the TiN thin film and the TaON thin film at a CVD chamber temperature around 500xc2x0 C. As a result, oxygen in the TaON thin film migrates to the TiN thin film, whereby a depletion of oxygen occurs within the TaON thin film. Also, there is an increase in leakage current in the capacitor comprised of the TaON thin film.
Therefore, the present invention has been made in order to solve the above-mentioned problems in the related art. The present invention provides a method for manufacturing a capacitor in a semiconductor device, which is capable of preventing deterioration of the dielectric film while suppressing the generation of leakage current in the capacitor.
In accordance with one aspect, the present invention provides a method for manufacturing a capacitor in a semiconductor device, comprising steps of: forming a lower electrode on a semiconductor substrate; forming a nitride film over the lower electrode; forming an amorphous TaON thin film over the nitride film; subjecting the amorphous TaON thin film to a thermal treatment at a high temperature to effect a crystallization thereof; and forming a laminated structure composed of a TiON film and a doped silicon film for an upper electrode over the crystallized TaON thin film.
In accordance with another aspect, the present invention provides a method for manufacturing a capacitor in a semiconductor device, comprising steps of: forming a lower electrode made of a conductive polysilicon film or a conductive amorphous silicon film on a semiconductor substrate; forming a nitride film over the lower electrode; forming an amorphous TaON thin film over the nitride film; crystallizing the TaON thin film by using a furnace in a batch type furnace (batch furnace) or a rapid thermal treatment; and forming a laminated structure composed of a TiON film and a doped silicon film for an upper electrode over the crystallized TaON thin film.